Setup Web Single Sign-On (SSO)

Keystone Changes

1. Update trusted_dashboard in keystone.conf.

Specify URLs of trusted horizon servers. This value may be repeated multiple times. This setting ensures that keystone only sends token data back to trusted servers. This is performed as a precaution, specifically to prevent man-in-the-middle (MITM) attacks.

[federation]
trusted_dashboard = http://acme.horizon.com/auth/websso/
trusted_dashboard = http://beta.horizon.com/auth/websso/

2. Update httpd vhost file with websso information.

The /v3/auth/OS-FEDERATION/websso/<protocol> and /v3/auth/OS-FEDERATION/identity_providers/{idp_id}/protocols/{protocol_id}/websso routes must be protected by the chosen httpd module. This is performed so the request that originates from horizon will use the same identity provider that is configured in keystone.

Warning

By using the IdP specific route, a user will no longer leverage the Remote ID of a specific Identity Provider, and will be unable to verify that the Identity Provider is trusted, the mapping will remain as the only means to controlling authorization.

If mod_shib is used, then use the following as an example:

<VirtualHost *:5000>

    ...

    <Location ~ "/v3/auth/OS-FEDERATION/websso/saml2">
      AuthType shibboleth
      Require valid-user
      ...
    </Location>
    <Location ~ "/v3/auth/OS-FEDERATION/identity_providers/idp_1/protocols/saml2/websso">
      AuthType shibboleth
      Require valid-user
      ...
    </Location>
</VirtualHost>

If mod_auth_openidc is used, then use the following as an example:

<VirtualHost *:5000>

    OIDCRedirectURI http://localhost:5000/v3/auth/OS-FEDERATION/websso/redirect
    OIDCRedirectURI http://localhost:5000/v3/auth/OS-FEDERATION/identity_providers/idp_1/protocol/oidc/websso/redirect

    ...

    <Location ~ "/v3/auth/OS-FEDERATION/websso/oidc">
      AuthType openid-connect
      Require valid-user
      ...
    </Location>
    <Location ~ "/v3/auth/OS-FEDERATION/identity_providers/idp_1/protocols/oidc/websso">
      AuthType openid-connect
      Require valid-user
      ...
    </Location>
</VirtualHost>

If mod_auth_kerb is used, then use the following as an example:

<VirtualHost *:5000>

    ...

    <Location ~ "/v3/auth/OS-FEDERATION/websso/kerberos">
      AuthType Kerberos
      AuthName "Acme Corporation"
      KrbMethodNegotiate on
      KrbMethodK5Passwd off
      Krb5Keytab /etc/apache2/http.keytab
      ...
    </Location>
    <Location ~ "/v3/auth/OS-FEDERATION/identity_providers/idp_1/protocols/kerberos/websso">
      AuthType Kerberos
      AuthName "Acme Corporation"
      KrbMethodNegotiate on
      KrbMethodK5Passwd off
      Krb5Keytab /etc/apache2/http.keytab
      ...
    </Location>
</VirtualHost>

If mod_auth_mellon is used, then use the following as an example:

<VirtualHost *:5000>

    ...

    <Location ~ "/v3/auth/OS-FEDERATION/websso/saml2">
      AuthType Mellon
      MellonEnable auth
      Require valid-user
      ...
    </Location>
    <Location ~ "/v3/auth/OS-FEDERATION/identity_providers/idp_1/protocols/saml2/websso">
      AuthType Mellon
      MellonEnable auth
      Require valid-user
      ...
    </Location>
</VirtualHost>

Note

If you are also using SSO via the API, don’t forget to make the Location settings match your configuration used for the keystone identity provider location: /v3/OS-FEDERATION/identity_providers/<idp>/protocols/<protocol>/auth

3. Update remote_id_attribute in keystone.conf.

A remote id attribute indicates the header to retrieve from the WSGI environment. This header contains information about the identity of the identity provider. For mod_shib this would be Shib-Identity-Provider, for mod_auth_openidc, this could be HTTP_OIDC_ISS. For mod_auth_mellon, this could be MELLON_IDP.

It is recommended that this option be set on a per-protocol basis.

[saml2]
remote_id_attribute = Shib-Identity-Provider
[oidc]
remote_id_attribute = HTTP_OIDC_ISS

Alternatively, a generic option may be set at the [federation] level.

[federation]
remote_id_attribute = HTTP_OIDC_ISS

4. Set remote_ids for a keystone identity provider using the API or CLI.

A keystone identity provider may have multiple remote_ids specified, this allows the same keystone identity provider resource to be used with multiple external identity providers. For example, an identity provider resource university-idp, may have the following remote_ids: ['university-x', 'university-y', 'university-z']. This removes the need to configure N identity providers in keystone.

This can be performed using the OS-FEDERATION API: PATCH /OS-FEDERATION/identity_providers/{idp_id}

Or by using the OpenStackClient CLI:

$ openstack identity provider set --remote-id <remote-id>  <idp-id>

Note

Remote IDs are globally unique. Two identity providers cannot be associated with the same remote ID. Once authenticated with the external identity provider, keystone will determine which identity provider and mapping to use based on the protocol and the value returned from the remote_id_attribute key.

For example, if our identity provider is google, the mapping used is google_mapping and the protocol is oidc. The identity provider’s remote IDs would be: [accounts.google.com]. The remote_id_attribute value may be set to HTTP_OIDC_ISS, since this value will always be accounts.google.com.

The motivation for this approach is that there will always be some data sent by the identity provider (in the assertion or claim) that uniquely identifies the identity provider. This removes the requirement for horizon to list all the identity providers that are trusted by keystone.

Horizon Changes

Note

Django OpenStack Auth version 1.2.0 or higher is required for these steps.

Identity provider and federation protocol specific webSSO is only available in Django OpenStack Auth version 2.0.0 or higher.

1. Set the Identity Service version to 3

Ensure the OPENSTACK_API_VERSIONS option in horizon’s local_settings.py has been updated to indicate that the identity version to use is 3.

OPENSTACK_API_VERSIONS = {
  "identity": 3,
}

2. Authenticate against Identity Server v3.

Ensure the OPENSTACK_KEYSTONE_URL option in horizon’s local_settings.py has been updated to point to a v3 URL.

OPENSTACK_KEYSTONE_URL = "http://localhost:5000/v3"

3. Set the WEBSSO_ENABLED option.

Ensure the WEBSSO_ENABLED option is set to True in horizon’s local_settings.py file, this will provide users with an updated login screen for horizon.

WEBSSO_ENABLED = True

4. (Optional) Create a list of authentication methods with the WEBSSO_CHOICES option.

Within horizon’s settings.py file, a list of supported authentication methods can be specified. The list includes Keystone federation protocols such as OpenID Connect and SAML, and also keys that map to specific identity provider and federation protocol combinations (as defined in WEBSSO_IDP_MAPPING). With the exception of credentials which is reserved by horizon, and maps to the user name and password used by keystone’s identity backend.

WEBSSO_CHOICES = (
      ("credentials", _("Keystone Credentials")),
      ("oidc", _("OpenID Connect")),
      ("saml2", _("Security Assertion Markup Language")),
      ("idp_1_oidc", "Acme Corporation - OpenID Connect"),
      ("idp_1_saml2", "Acme Corporation - SAML2")
    )

5. (Optional) Create a dictionary of specific identity provider and federation protocol combinations.

A dictionary of specific identity provider and federation protocol combinations. From the selected authentication mechanism, the value will be looked up as keys in the dictionary. If a match is found, it will redirect the user to a identity provider and federation protocol specific WebSSO endpoint in keystone, otherwise it will use the value as the protocol_id when redirecting to the WebSSO by protocol endpoint.

WEBSSO_IDP_MAPPING = {
      "idp_1_oidc": ("idp_1", "oidc"),
      "idp_1_saml2": ("idp_1", "saml2")
    }

Note

The value is expected to be a tuple formatted as: (<idp_id>, <protocol_id>).

6. (Optional) Specify an initial choice with the WEBSSO_INITIAL_CHOICE option.

The list set by the WEBSSO_CHOICES option will be generated in a drop-down menu in the login screen. The setting WEBSSO_INITIAL_CHOICE will automatically set that choice to be highlighted by default.

WEBSSO_INITIAL_CHOICE = "credentials"